Wordpress - Taxonomias Drop Down

<?php
/* DROPDOWN PARA MOSTRAR TAXONOMIAS "MÃES" EM QUALQUER PÁGINA */
                function get_terms_dropdown_maes($taxonomies, $args) {
                    $myterms = get_terms($taxonomies, $args);
                    $output = '<select name="NOME-DA-TAXONOMIA">';
                    $output .='<option value="#">Filtrar por categoria</option>';
                    foreach ($myterms as $term) {
                        $term_slug = $term->slug;
                        $term_name = $term->name;
                        $link = $term_slug;
                        $output .='<option value="' . $link . '">' . $term_name . '</option>';
                    }
                    $output .='</select>';
                    return $output;
                }
                ?>
                <form action="<?php bloginfo('url'); ?>" method="get">
                    <?php
                    $taxonomies = array('NOME-DA-TAXONOMIA');
                    $args = array('orderby' => 'name', 'hide_empty' => true, 'parent' => 0);
                    $select = get_terms_dropdown_tipo($taxonomies, $args);
                    $select = preg_replace("#<select([^>]*)>#", "<select$1 onchange='return this.form.submit()'>", $select);
                    echo $select;
                    ?>
                </form>
/************************************************************/

<?PHP
/* DROPDOWN PARA MOSTRAR APENAS TAXONOMIAS FILHAS NA PÁGINA DA "MÃE"  */

function get_terms_dropdown_filhas($taxonomies, $args) {
                    $current_term = get_term_by('slug', get_query_var('term'), get_query_var('taxonomy'));
                    $output = '<select name="NOME-DA-TAXONOMIA">';
                    $output .='<option value="#">Sub-categorias</option>';
                    $termID = $current_term->term_id;
                    $taxonomyName = "tipo";
                    $termchildren = get_term_children($termID, $taxonomyName);
                    foreach ($termchildren as $child) {
                        $term = get_term_by('id', $child, $taxonomyName);
                        $slug = $term->slug;
                        $term_name = $term->name;
                        $output .='<option value="' . $slug . '">' . $term_name . '</option>';
                    }
                    $output .='</select>';
                    return $output;
                }
                $term = get_term_by('slug', get_query_var('term'), get_query_var('taxonomy'));
                if ($term->parent == 0) { /* se for uma página "mãe" */
                    ?>
                    <form action="<?php bloginfo('url'); ?>" method="get">
                        <?php
                        $taxonomyName = "NOME-DA-TAXONOMIA";
                        $select = get_terms_dropdown_tipo_terms($termID, $taxonomyName);
                        $select = preg_replace("#<select([^>]*)>#", "<select$1 onchange='return this.form.submit()'>", $select);
                        echo $select;
                        ?>
                    </form>
                <?php } else { /* se for uma página de taxonomia filha */?>
                <form action="<?php bloginfo('url'); ?>" method="get">
                    <select name="NOME-DA-TAXONOMIA">
                        <option value="#">Sub-categorias</option>
                        <option value="#">Não há sub-categorias</option>
                    </select>
                </form>
                <?php } ?>